Understanding Maps

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Understanding Maps

• Biman Basu
• Ex-Editor, Science Reporter
• bimanbasu_at_gmail.com

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What Is A Map?

• A map is simply a plan of the ground on paper,
  as seen from directly above.
• It may be a representation of a country, a city,
  a neighbourhood, or a village.
• Or even the layout of an exhibition, a shopping
  complex, or a nature park.
• Maps on a globe show continents and oceans as
  seen from space directly above.

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Why Do We Need To Understand Maps?

• To find our way around a city.
• To find the location of specific places in a new
  city.
• To find the shortest route to a specific spot.
• To find out locations of petrol pumps and eating
  places on a highway.
• In case of emergency, to find out the nearest
  hospital/medical aid.

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What Are Maps For?

• Maps are not just for doing geography.
• We use maps often in everyday life, for locating
  places or landmarks.
• We also use maps to locate a room in a museum, a
  department in the university campus, or an animal
  enclosure in a zoo.
• Road maps are perhaps the most widely used maps
  today.
• Map reading forms a basic lifelong literacy skill.

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What Does A Map Contain?
Boundaries of districts, states, countries and
names of important places and locations.
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Map Symbols

• Objects and features are represented on a map by
  symbols.
• So in order to be able to read maps it is
  necessary to understand the symbols.
• Most of the symbols used in maps are universal,
  but many are used in special maps.

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Map Symbols
Standard symbols show the location of various
features along with a key.
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More Map Symbols
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Map Scales
Scale refers to the relationship between the size
of the map and the actual size of area that is
mapped, or relative distance.
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Grid Lines
A grid system of lines helps pinpoint a location
quickly and estimate distances.
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Contour Lines
Contour lines show relief and the steepness of
the land.
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Orienting The Map
The most common cartographic convention is that
North is at the top of a map. If the map is not
oriented with North at the top then an arrow
pointing North is usually added.
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Polar Maps
Maps of the Arctic or Antarctic regions are
conventionally centred on the pole, in which case
the direction north would be towards or away from
the centre of the map, respectively.
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Map Projections

• The Earth is a spherical body with a curved
  surface. But a map is essentially a flat surface.
  In order to turn the Earths curved surface into
  the flat surface of a map several methods of
  projection are used. The most common are
• Cylindrical Projections
• Azimuthal Projections
• Conical Projections
• The choice of the class of a map projection is
  made on the basis of the shape and size of the
  geographical area to be mapped. Every projection
  method leads to some distortion in the shape or
  area of the nations.

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Map Projections
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Cylindrical Projection
Cylindrical projection maps, such as the Marcator
projection map, in which a cylinder which is
wrapped around the Earth at the
Equator, are often used for complete world maps.
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Azimuthal Projection
Azimuthal projection maps, in which the Earth's
surface is projected onto a flat surface
placed against the globe, are most often used to
map polar regions, but may be used to represent
any part of Earth's surface.
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Conical Projection
Conical projection maps, in which the Earth's
surface is projected onto a cone placed on the
globe with its point over
one of the Earth's poles, poles, are best suited
for maps of polar and mid-latitude regions.
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Equal-Area Projection
Equal-area map projection is a map projection in
which quadrilaterals formed by meridians and
parallels have an area on the map proportional to
their area on the globe.
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Types of Maps

• Topographic or physical maps show physical
  features of the Earth's land surface.
• Thematic maps, display the spatial distribution
  of a single attribute such as soil type,
  vegetation, geology, land use, population
  density, etc.
• Cadastral maps describe boundaries and ownership
  of land and are an important component of land
  administration in most countries.

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Topographic Map
Topographic maps show physical features of the
land. Here different levels of the land are shown
in different colours. Green shows the lowest
lands and light purple and white the highest land
elevations.
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3D Topographic Map (Relief Map)
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Thematic Maps

• The most widely touted example of early thematic
  mapping comes from London physician John Snow.
• Snows cholera map in 1854 is the best known
  example of using thematic maps for analysis.
• Essentially, his technique and methodology
  reflects principles of a geographic information
  system.

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Snows Cholera Map 1854
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Thematic Maps
Map showing population density in India
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Thematic Maps
Map showing wildlife sanctuaries in India.
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Thematic Maps
Map showing the major river systems in India. It
also shows the catchment areas
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Thematic Maps
Seismic zones indicate the proneness of a region
to earthquakes. Zone I, shown in blue, are the
least earthquake-prone whereas Zone IV regions
are the most prone.
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Indian Monsoon
The map shows rainfall pattern during the months
of June to September. The blue lines are
isohyets - lines joining the points on the map
having the same amount of rainfall during a given
period.
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Cadastral Map
Cadastral maps describe boundaries and ownership
and are an important component of land
administration in most countries.
Digital cadastral maps are common today.
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Remote Sensing Maps

• Modern remote sensing maps are prepared on the
  basis of satellite imagery in which multispectral
  and infrared sensing are used.
• Multispectral sensing allows identification of
  different features on ground on the basis of
  their spectral characteristics (in different
  wavelengths).
• Using infrared sensing cartographers can detect
  the temperatures of different objects on the
  ground, which can help when mapping living
  objects, such as plant and animal distribution.
• Living organisms generate heat, while dead
  objects generally do not.
• Infrared sensing is commonly used when studying
  crops, and the health of different habitats.
• Remote sensing maps usually show ground features
  in false colour.

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Remote Sensing Map
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Satellite Maps vs Cartographic Maps
Satellite
Cartographic
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Geographic Information System (GIS)

• GIS is a computer-based technology for the
  storage, manipulation, and analysis of
  geographically referenced information.
• It is composed of software, hardware, and data.
  The notion of data layer and overlay operation
  lies at the heart of most software designed for
  geographic information systems.
• By putting maps and other kinds of spatial
  information into digital form, GIS allows us to
  manipulate and display geographical knowledge in
  new and exciting ways.

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Geographic Information System (GIS)
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Applications of GIS

• Resource management
• Modelling terrain, building roads and bridges.
• Strategic planning by integrating intelligence
  information on enemy targets.
• Environmental impact assessment
• Scientific investigations
• Such applications have been facilitated
  through the integration of geographic information
  systems with global positioning systems.

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Map Reading Essentials

• Understand the type of map.
• Hold the map with correct orientation.
• Understand the symbols.
• Find out the scale of the map.
• Try to locate a place of interest.
• Find out its distance from your home using the
  map scale.
• Find out how many types of map you can read with
  ease.

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. Thank You!